Use of sludge from the vehicle industry and its encapsulation of toxic metals in ceramic products.

ABSTRACT

Despite the various existing studies with wastes from wastewater treatment plants for the production of bricks, there is still a lack of further studies on the technological characterization and application only of hazardous industrial wastes from the treatment of wastewater from the metal-processing automotive industry in the stabilization/solidification with ceramic materials. Therefore, the objective of this work was to evaluate the use of waste from the treatment of wastewater from the metal processing automotive industry for the production of red ceramics by evaluating the mechanical behavior and the potential for encapsulation of contaminants. The waste was originally classified as Class I-Hazardous due to the presence of Se. A clay with a clayey-silty character was used to produce ceramic test specimens by pressing and calcining at 950 °C. In the production of these test specimens, the clay was replaced with 0%, 5%, and 10% waste, and the mechanical properties of linear shrinkage, apparent porosity, water absorption, and three-point flexural strength of the test specimens, as well as the mineralogical, chemical, and microstructural composition such as the leaching of contaminants and potential encapsulation of all test specimens were evaluated. The results showed that after incorporation into the red ceramic, the wastes led to a reduction in flexural strength associated with greater water absorption and porosity, the higher the incorporated percentage. Changes in mineralogy and chemical composition were observed but did not affect microstructure and mechanical properties. The samples did not show metal leaching above national and international standards for toxicity and limits for groundwater and human consumption. It can be concluded that the use of up to 5% of the waste as a replacement for clay meets the requirements for good mechanical performance and encapsulation of the metals originally present in the waste.